British Transport Police (BTP) detectives are asking for the public’s help in identifying a man following a sexual assault on a train between Putney and Mortlake.

As part of their appeal for information, investigators have released CCTV images of a man they want to speak to.

The incident took place around midday on Sunday, 15 May after the 24-year-old victim and a friend caught a train at Putney.

Shortly after they boarded, a man approached and sat opposite them. When the train arrived at Mortlake a few minutes later, he stood up and approached the victim before touching her indecently.

The man, who had previously travelled to Putney from Clapham Junction, then left the train and fled the station.

Investigators have conducted several lines of enquiry into the incident, including taking witness statements, viewing CCTV in the area and circulating the images on police intelligence systems but to no avail so far.

Detective Constable Andy Parkinson, of BTP’s Public Protection Unit, said: “We are treating this incident very seriously. This was a distressing and intimidating experience for the victim and we are determined to trace the person responsible. If you recognise the man pictured, or have any information about the incident that could assist us, I would like to hear from you.”